Rapid start fluorescent lamps are very popular for lighting purposes, especially in offices, work places, business and homes. Rapid start ballasts offer some technical advantages over the instant start ballast, such as an increase in lamp life expectancy because the turn on process of the rapid start ballast causes less deterioration in the lamps. Rapid start ballasts achieve the lighting of the lamps by heating the filaments in the lamp terminals using a current so that an electrical flow may begin through the fluorescent tube.
Ballasts, such as rapid start ballasts, control the intensity of the electrical flow through the lamp at a nearly constant value and allow an intense luminosity which is close to the nominal power of the lamps used.
Some rapid start ballasts are designed to allow control of the illumination intensity using elements such as light sensors, presence sensors, or other devices outside of the ballast. The aforementioned is performed by incorporating these elements to regulate the electrical flow of the lamp, where the electrical current affects the luminous intensity of the lamp.
In one conventional approach, a rapid start ballast has an entry port to turn on or off selected lamps in an array of lamps. By selectively turning on or off ones of the lamps, the ballast controls the total luminosity of the array of lamps. However, this approach changes the lighting pattern of the array of lamps, losing uniformity in the intensity in the illuminated area.
In another conventional approach, a rapid start ballast provides control of illumination intensity though use of a frequency variation element. In one example, a rapid start ballast contains an element that regulates the current which flows through the lamps with a frequency variation technique. The frequency variation technique moves an operating frequency closer or farther away from a resonance frequency to control the luminous intensity of a lamp. Another conventional technique includes changing the relation of the current amplitude in the two half cycles of a sinusoidal waveform, regulating the current and the luminosity.
There is a need for an efficient and effective way to provide luminosity control for a fluorescent lamp installed with a rapid start ballast.